Interactive shell. A shell is “interactive”
if this option is used or if both standard input and standard error are
attached to a tty(4). An
interactive shell has job control enabled, ignores the
SIGINT,
SIGQUIT, and
SIGTERM signals, and prints prompts
before reading input (see the PS1 and
PS2 parameters). For non-interactive
shells, the trackall option is on by default
(see the set command below).

Login shell. If the basename the shell is called with (i.e.
argv[0]) starts with ‘-’ or if this
option is used, the shell is assumed to be a login shell and the shell
reads and executes the contents of
/etc/profile and
$HOME/.profile if they exist and are
readable.

Privileged shell. A shell is “privileged” if
this option is used or if the real user ID or group ID does not match the
effective user ID or group ID (see
getuid(2) and
getgid(2)). A privileged
shell does not process $HOME/.profile nor the
ENV parameter (see below). Instead, the
file /etc/suid_profile is processed. Clearing
the privileged option causes the shell to set its effective user ID (group
ID) to its real user ID (group ID).

Restricted shell. A shell is “restricted” if
this option is used; if the basename the shell was invoked with was
“rksh”; or if the SHELL
parameter is set to “rksh”. The following restrictions come
into effect after the shell processes any profile and
ENV files:

The shell reads commands from standard input; all
non-option arguments are positional parameters.

In addition to the above, the options described in the
set built-in command can also be used on the
command line: both
[-+abCefhkmnuvXx] and
[-+ooption] can be used for single letter
or long options, respectively.

If neither the -c nor the
-s option is specified, the first non-option
argument specifies the name of a file the shell reads commands from. If there
are no non-option arguments, the shell reads commands from the standard input.
The name of the shell (i.e. the contents of $0) is determined as follows: if
the -c option is used and there is a non-option
argument, it is used as the name; if commands are being read from a file, the
file is used as the name; otherwise, the basename the shell was called with
(i.e. argv[0]) is used.

If the ENV parameter is set when an
interactive shell starts (or, in the case of login shells, after any profiles
are processed), its value is subjected to parameter, command, arithmetic, and
tilde (‘~’) substitution and the resulting file (if any) is read
and executed. In order to have an interactive (as opposed to login) shell
process a startup file, ENV may be set and
exported (see below) in $HOME/.profile - future
interactive shell invocations will process any file pointed to by
$ENV:

export ENV=$HOME/.kshrc

$HOME/.kshrc is then free to specify instructions
for interactive shells. For example, the global configuration file may be
sourced:

. /etc/ksh.kshrc

The above strategy may be employed to keep setup procedures for login shells in
$HOME/.profile and setup procedures for
interactive shells in $HOME/.kshrc. Of course,
since login shells are also interactive, any commands placed in
$HOME/.kshrc will be executed by login shells
too.

The exit status of the shell is 127 if the command file specified on the command
line could not be opened, or non-zero if a fatal syntax error occurred during
the execution of a script. In the absence of fatal errors, the exit status is
that of the last command executed, or zero, if no command is executed.

The shell begins parsing its input by breaking it into
words. Words, which are sequences of characters,
are delimited by unquoted whitespace characters (space, tab, and newline) or
meta-characters (‘<’,
‘>’,
‘|’,
‘;’,
‘(’,
‘)’, and
‘&’). Aside from delimiting words,
spaces and tabs are ignored, while newlines usually delimit commands. The
meta-characters are used in building the following
tokens:
‘<’,
‘<&’,
‘<<’,
‘>’,
‘>&’,
‘>>’, etc. are used to
specify redirections (see
Input/output
redirection below); ‘|’ is used to
create pipelines; ‘|&’ is used to
create co-processes (see
Co-processes below);
‘;’ is used to separate commands;
‘&’ is used to create asynchronous
pipelines; ‘&&’ and
‘||’ are used to specify conditional
execution; ‘;;’ is used in
case statements; ‘(( ..
))’ is used in arithmetic expressions; and lastly,
‘( .. )’ is used to create subshells.

Whitespace and meta-characters can be quoted individually using a backslash
(‘\’), or in groups using double (‘"’) or
single (‘'’) quotes. The following characters are also treated
specially by the shell and must be quoted if they are to represent themselves:
‘\’,
‘"’,
‘'’,
‘#’,
‘$’,
‘`’,
‘~’,
‘{’,
‘}’,
‘*’,
‘?’, and
‘[’. The first three of these are the
above mentioned quoting characters (see
Quoting below);
‘#’, if used at the beginning of a word,
introduces a comment — everything after the
‘#’ up to the nearest newline is
ignored; ‘$’ is used to introduce
parameter, command, and arithmetic substitutions (see
Substitution below);
‘`’ introduces an old-style command
substitution (see
Substitution below);
‘~’ begins a directory expansion (see
Tilde expansion below);
‘{’ and
‘}’ delimit
csh(1)-style alternations (see
Brace expansion below);
and finally, ‘*’,
‘?’, and
‘[’ are used in file name generation
(see File name
patterns below).

As words and tokens are parsed, the shell builds commands, of which there are
two basic types: simple-commands, typically
programs that are executed, and
compound-commands, such as
for and if
statements, grouping constructs, and function definitions.

A simple-command consists of some combination of parameter assignments (see
Parameters below),
input/output redirections (see
Input/output
redirections below), and command words; the only restriction is that
parameter assignments come before any command words. The command words, if
any, define the command that is to be executed and its arguments. The command
may be a shell built-in command, a function, or an external command (i.e. a
separate executable file that is located using the
PATH parameter; see
Command execution
below).

All command constructs have an exit status. For external commands, this is
related to the status returned by
wait(2) (if the command could not
be found, the exit status is 127; if it could not be executed, the exit status
is 126). The exit status of other command constructs (built-in commands,
functions, compound-commands, pipelines, lists, etc.) are all well-defined and
are described where the construct is described. The exit status of a command
consisting only of parameter assignments is that of the last command
substitution performed during the parameter assignment or 0 if there were no
command substitutions.

Commands can be chained together using the
‘|’ token to form pipelines, in which
the standard output of each command but the last is piped (see
pipe(2)) to the standard input of
the following command. The exit status of a pipeline is that of its last
command. A pipeline may be prefixed by the
‘!’ reserved word, which causes the exit
status of the pipeline to be logically complemented: if the original status
was 0, the complemented status will be 1; if the original status was not 0,
the complemented status will be 0.

Lists of commands can be created by separating
pipelines by any of the following tokens:
‘&&’,
‘||’,
‘&’,
‘|&’, and
‘;’. The first two are for conditional
execution: “cmd1&&cmd2” executes
cmd2 only if the exit status of
cmd1 is zero;
‘||’ is the opposite —
cmd2 is executed only if the exit status of
cmd1 is non-zero.
‘&&’ and
‘||’ have equal precedence which is
higher than that of ‘&’,
‘|&’, and
‘;’, which also have equal precedence.
The ‘&&’ and
‘||’ operators are
“left-associative”. For example, both of these commands will
print only “bar”:

$ false && echo foo || echo bar
$ true || echo foo && echo bar

The ‘&’ token causes the preceding
command to be executed asynchronously; that is, the shell starts the command
but does not wait for it to complete (the shell does keep track of the status
of asynchronous commands; see Job
control below). When an asynchronous command is started when job control
is disabled (i.e. in most scripts), the command is started with signals
SIGINT and
SIGQUIT ignored and with input redirected
from /dev/null (however, redirections specified
in the asynchronous command have precedence). The
‘|&’ operator starts a co-process
which is a special kind of asynchronous process (see
Co-processes below). A
command must follow the ‘&&’ and
‘||’ operators, while it need not follow
‘&’,
‘|&’, or
‘;’. The exit status of a list is that
of the last command executed, with the exception of asynchronous lists, for
which the exit status is 0.

Compound commands are created using the following reserved words. These words
are only recognized if they are unquoted and if they are used as the first
word of a command (i.e. they can't be preceded by parameter assignments or
redirections):

case esac in until (( }
do fi name while ))
done for select ! [[
elif function then ( ]]
else if time ) {

Note: Some shells (but not this one) execute
control structure commands in a subshell when one or more of their file
descriptors are redirected, so any environment changes inside them may fail.
To be portable, the exec statement should be used
instead to redirect file descriptors before the control structure.

In the following compound command descriptions, command lists (denoted as
list) that are followed by reserved words must
end with a semicolon, a newline, or a (syntactically correct) reserved word.
For example, the following are all valid:

The case statement attempts to
match word against a specified
pattern; the
list associated with the first
successfully matched pattern is executed. Patterns used in
case statements are the same as those used
for file name patterns except that the restrictions regarding
‘.’ and
‘/’ are dropped. Note that any
unquoted space before and after a pattern is stripped; any space within a
pattern must be quoted. Both the word and the patterns are subject to
parameter, command, and arithmetic substitution, as well as tilde
substitution. For historical reasons, open and close braces may be used
instead of in and
esac e.g. case $foo
{ *) echo bar; }. The exit status of a
case statement is that of the executed
list; if no
list is executed, the exit status is
zero.

For each word in the
specified word list, the parameter name
is set to the word and list is executed.
If in is not used to specify a word list, the
positional parameters ($1, $2, etc.) are used instead. For historical
reasons, open and close braces may be used instead of
do and done e.g.
for i; { echo $i; }. The exit status of a
for statement is the last exit status of
list; if
list is never executed, the exit status
is zero.

If the exit status of the first
list is zero, the second
list is executed; otherwise, the
list following the
elif, if any, is executed with similar
consequences. If all the lists following the
if and elifs
fail (i.e. exit with non-zero status), the
list following the
else is executed. The exit status of an
if statement is that of non-conditional
list that is executed; if no
non-conditional list is executed, the
exit status is zero.

The select statement provides
an automatic method of presenting the user with a menu and selecting from
it. An enumerated list of the specified
word(s) is printed on standard error,
followed by a prompt (PS3: normally
‘#? ’). A number corresponding to one of the
enumerated words is then read from standard input,
name is set to the selected word (or
unset if the selection is not valid),
REPLY is set to what was read
(leading/trailing space is stripped), and
list is executed. If a blank line (i.e.
zero or more IFS characters) is
entered, the menu is reprinted without executing
list.

When list completes, the enumerated list is
printed if REPLY is
NULL, the prompt is printed, and so on.
This process continues until an end-of-file is read, an interrupt is
received, or a break statement is executed
inside the loop. If “in word ...” is omitted, the positional
parameters are used (i.e. $1, $2, etc.). For historical reasons, open and
close braces may be used instead of do and
done e.g. select i;
{ echo $i; }. The exit status of a select
statement is zero if a break statement is
used to exit the loop, non-zero otherwise.

A while is a pre-checked loop.
Its body is executed as often as the exit status of the first
list is zero. The exit status of a
while statement is the last exit status of
the list in the body of the loop; if the
body is not executed, the exit status is zero.

Defines the function name
(see Functions below). Note
that redirections specified after a function definition are performed
whenever the function is executed, not when the function definition is
executed.

Similar to the test and
[...] commands (described later), with the
following exceptions:

Field splitting and file name generation are not
performed on arguments.

The -a (AND) and
-o (OR) operators are replaced with
‘&&’ and
‘||’, respectively.

Operators (e.g.
‘-f’, ‘=’,
‘!’) must be unquoted.

The second operand of the ‘!=’ and
‘=’ expressions are patterns (e.g. the comparison
[[ foobar = f*r ]] succeeds).

There are two additional binary operators,
‘<’ and
‘>’, which return true if
their first string operand is less than, or greater than, their second
string operand, respectively.

The single argument form of
test, which tests if the argument has a
non-zero length, is not valid; explicit operators must always be used
e.g. instead of [str] use
[[ -nstr]].

Parameter, command, and arithmetic substitutions are
performed as expressions are evaluated and lazy expression evaluation
is used for the ‘&&’ and
‘||’ operators. This means that
in the following statement, $(< foo)
is evaluated if and only if the file foo
exists and is readable:

Quoting is used to prevent the shell from treating characters or words
specially. There are three methods of quoting. First,
‘\’ quotes the following character,
unless it is at the end of a line, in which case both the
‘\’ and the newline are stripped.
Second, a single quote (‘'’) quotes everything up to the next
single quote (this may span lines). Third, a double quote
(‘"’) quotes all characters, except
‘$’,
‘`’ and
‘\’, up to the next unquoted double
quote. ‘$’ and
‘`’ inside double quotes have their
usual meaning (i.e. parameter, command, or arithmetic substitution) except no
field splitting is carried out on the results of double-quoted substitutions.
If a ‘\’ inside a double-quoted string
is followed by ‘\’,
‘$’,
‘`’, or
‘"’, it is replaced by the second
character; if it is followed by a newline, both the
‘\’ and the newline are stripped;
otherwise, both the ‘\’ and the
character following are unchanged.

There are two types of aliases: normal command aliases and tracked aliases.
Command aliases are normally used as a short hand for a long or often used
command. The shell expands command aliases (i.e. substitutes the alias name
for its value) when it reads the first word of a command. An expanded alias is
re-processed to check for more aliases. If a command alias ends in a space or
tab, the following word is also checked for alias expansion. The alias
expansion process stops when a word that is not an alias is found, when a
quoted word is found, or when an alias word that is currently being expanded
is found.

Tracked aliases allow the shell to remember where it found a particular command.
The first time the shell does a path search for a command that is marked as a
tracked alias, it saves the full path of the command. The next time the
command is executed, the shell checks the saved path to see that it is still
valid, and if so, avoids repeating the path search. Tracked aliases can be
listed and created using alias -t. Note that
changing the PATH parameter clears the
saved paths for all tracked aliases. If the
trackall option is set (i.e.
set -otrackall or
set -h), the shell tracks all commands. This
option is set automatically for non-interactive shells. For interactive
shells, only the following commands are automatically tracked:
cat(1),
cc(1),
chmod(1),
cp(1),
date(1),
ed(1),
emacs,
grep(1),
ls(1),
mail(1),
make(1),
mv(1),
pr(1),
rm(1),
sed(1),
sh(1),
vi(1), and
who(1).

The first step the shell takes in executing a simple-command is to perform
substitutions on the words of the command. There are three kinds of
substitution: parameter, command, and arithmetic. Parameter substitutions,
which are described in detail in the next section, take the form
$name or
${...}; command substitutions take the form
$(command) or
`command`; and arithmetic substitutions take
the form $((expression)).

If a substitution appears outside of double quotes, the results of the
substitution are generally subject to word or field splitting according to the
current value of the IFS parameter. The
IFS parameter specifies a list of
characters which are used to break a string up into several words; any
characters from the set space, tab, and newline that appear in the
IFS characters are called “IFS
whitespace”. Sequences of one or more
IFS whitespace characters, in combination
with zero or one non-IFS whitespace
characters, delimit a field. As a special case, leading and trailing
IFS whitespace is stripped (i.e. no leading
or trailing empty field is created by it); leading
non-IFS whitespace does create an empty
field.

Example: If IFS is set to
“<space>:”, and VAR is set to
“<space>A<space>:<space><space>B::D”,
the substitution for $VAR results in four fields: ‘A’,
‘B’, ‘’ (an empty field), and ‘D’.
Note that if the IFS parameter is set to
the NULL string, no field splitting is
done; if the parameter is unset, the default value of space, tab, and newline
is used.

Also, note that the field splitting applies only to the immediate result of the
substitution. Using the previous example, the substitution for $VAR:E results
in the fields: ‘A’, ‘B’, ‘’, and
‘D:E’, not ‘A’, ‘B’,
‘’, ‘D’, and ‘E’. This behavior is
POSIX compliant, but incompatible with some other shell implementations which
do field splitting on the word which contained the substitution or use
IFS as a general whitespace delimiter.

The results of substitution are, unless otherwise specified, also subject to
brace expansion and file name expansion (see the relevant sections below).

A command substitution is replaced by the output generated by the specified
command, which is run in a subshell. For
$(command) substitutions, normal quoting
rules are used when command is parsed;
however, for the `command` form, a
‘\’ followed by any of
‘$’,
‘`’, or
‘\’ is stripped (a
‘\’ followed by any other character is
unchanged). As a special case in command substitutions, a command of the form
<file is interpreted to mean substitute
the contents of file. Note that
$(< foo) has the same effect as
$(cat foo), but it is carried out more
efficiently because no process is started.

Arithmetic substitutions are replaced by the value of the specified expression.
For example, the command echo $((2+3*4)) prints
14. See Arithmetic
expressions for a description of an expression.

Parameters are shell variables; they can be assigned values and their values can
be accessed using a parameter substitution. A parameter name is either one of
the special single punctuation or digit character parameters described below,
or a letter followed by zero or more letters or digits
(‘_’ counts as a letter). The latter
form can be treated as arrays by appending an array index of the form
[expr] where
expr is an arithmetic expression. Parameter
substitutions take the form $name,
${name}, or
${name
[expr] } where
name is a parameter name. If
expr is a literal
‘@’ then the named array is expanded
using the same quoting rules as ‘$@’,
while if expr is a literal
‘*’ then the named array is expanded
using the same quoting rules as ‘$*’. If
substitution is performed on a parameter (or an array parameter element) that
is not set, a null string is substituted unless the
nounset option (set-onounset or
set-u) is set, in
which case an error occurs.

Parameters can be assigned values in a number of ways. First, the shell
implicitly sets some parameters like
‘#’,
‘PWD’, and
‘$’; this is the only way the special
single character parameters are set. Second, parameters are imported from the
shell's environment at startup. Third, parameters can be assigned values on
the command line: for example, FOO=bar sets the
parameter “FOO” to “bar”; multiple parameter
assignments can be given on a single command line and they can be followed by
a simple-command, in which case the assignments are in effect only for the
duration of the command (such assignments are also exported; see below for the
implications of this). Note that both the parameter name and the
‘=’ must be unquoted for the shell to
recognize a parameter assignment. The fourth way of setting a parameter is
with the export,
readonly, and
typeset commands; see their descriptions in the
Command execution
section. Fifth, for and
select loops set parameters as well as the
getopts, read, and
set -A commands. Lastly, parameters can be
assigned values using assignment operators inside arithmetic expressions (see
Arithmetic
expressions below) or using the
${name=value}
form of the parameter substitution (see below).

Parameters with the export attribute (set using the
export or typeset-x commands, or by parameter assignments followed
by simple commands) are put in the environment (see
environ(7)) of commands run by
the shell as
name=value
pairs. The order in which parameters appear in the environment of a command is
unspecified. When the shell starts up, it extracts parameters and their values
from its environment and automatically sets the export attribute for those
parameters.

Modifiers can be applied to the ${name} form of
parameter substitution:

${name:-word}

If name is set and not
NULL, it is substituted; otherwise,
word is substituted.

${name:+word}

If name is set and not
NULL,
word is substituted; otherwise, nothing
is substituted.

${name:=word}

If name is set and not
NULL, it is substituted; otherwise, it
is assigned word and the resulting value
of name is substituted.

${name:?word}

If name is set and not
NULL, it is substituted; otherwise,
word is printed on standard error
(preceded by name:) and an error occurs
(normally causing termination of a shell script, function, or script
sourced using the ‘.’ built-in). If
word is omitted, the string
“parameter null or not set” is used instead.

In the above modifiers, the ‘:’ can be
omitted, in which case the conditions only depend on
name being set (as opposed to set and not
NULL). If
word is needed, parameter, command,
arithmetic, and tilde substitution are performed on it; if
word is not needed, it is not evaluated.

The following forms of parameter substitution can also be used:

${#name}

The number of positional parameters if
name is
‘*’,
‘@’, or not specified; otherwise the
length of the string value of parameter
name.

${#name[*]}

${#name[@]}

The number of elements in the array
name.

${name#pattern}

${name##pattern}

If pattern matches the
beginning of the value of parameter name,
the matched text is deleted from the result of substitution. A single
‘#’ results in the shortest match,
and two of them result in the longest match.

${name%pattern}

${name%%pattern}

Like ${..#..} substitution, but it deletes from the end of
the value.

The following special parameters are implicitly set by the shell and cannot be
set directly using assignments:

The name of the shell, determined as follows: the first
argument to ksh if it was invoked with the
-c option and arguments were given; otherwise
the file argument, if it was supplied; or
else the basename the shell was invoked with (i.e.
argv[0]). $0 is
also set to the name of the current script or the name of the current
function, if it was defined with the function
keyword (i.e. a Korn shell style function).

All positional parameters (except parameter 0) i.e. $1, $2,
$3, ... If used outside of double quotes, parameters are separate words
(which are subjected to word splitting); if used within double quotes,
parameters are separated by the first character of the
IFS parameter (or the empty string if
IFS is
NULL).

Same as $*, unless it is used
inside double quotes, in which case a separate word is generated for each
positional parameter. If there are no positional parameters, no word is
generated. $@ can be used to access
arguments, verbatim, without losing
NULL arguments or splitting arguments
with spaces.

When an external command is executed by the shell, this
parameter is set in the environment of the new process to the path of the
executed command. In interactive use, this parameter is also set in the
parent shell to the last word of the previous command. When
MAILPATH messages are evaluated, this
parameter contains the name of the file that changed (see the
MAILPATH parameter, below).

Search path for the cd
built-in command. It works the same way as
PATH for those directories not
beginning with ‘/’ or
‘.’ in
cd commands. Note that if
CDPATH is set and does not contain
‘.’ or contains an empty path, the current directory is not
searched. Also, the cd built-in command will
display the resulting directory when a match is found in any search path
other than the empty path.

Set to the number of columns on the terminal or window.
Currently set to the “cols” value as reported by
stty(1) if that value is
non-zero. This parameter is used by the interactive line editing modes,
and by the select,
set -o, and kill
-l commands to format information columns.

If the VISUAL parameter
is not set, this parameter controls the command-line editing mode for
interactive shells. See the VISUAL
parameter below for how this works.

Note: traditionally, EDITOR was used to
specify the name of an (old-style) line editor, such as
ed(1), and
VISUAL was used to specify a
(new-style) screen editor, such as
vi(1). Hence if
VISUAL is set, it overrides
EDITOR.

Like PATH, but used when
an undefined function is executed to locate the file defining the
function. It is also searched when a command can't be found using
PATH. See
Functions below for more
information.

A colon separated list of history settings. If
ignoredups is present, lines identical to the
previous history line will not be saved. If
ignorespace is present, lines starting with a
space will not be saved. Unknown settings are ignored.

The name of the file used to store command history. When
assigned to, history is loaded from the specified file. Also, several
invocations of the shell running on the same machine will share history if
their HISTFILE parameters all point to
the same file.

Note: If
HISTFILE isn't set, no history file is
used. This is different from the original Korn shell, which uses
$HOME/.sh_history.

A list of files to be checked for mail. The list is colon
separated, and each file may be followed by a
‘?’ and a message to be printed if
new mail has arrived. Command, parameter, and arithmetic substitution is
performed on the message and, during substitution, the parameter
$_ contains the name of the file. The default
message is “you have mail in $_”.

A colon separated list of directories that are searched
when looking for commands and files sourced using the ‘.’
command (see below). An empty string resulting from a leading or trailing
colon, or two adjacent colons, is treated as a ‘.’ (the
current directory).

The primary prompt for interactive shells. Parameter,
command, and arithmetic substitutions are performed, and the prompt string
can be customised using backslash-escaped special characters.

Note that since the command-line editors try to figure out how long the
prompt is (so they know how far it is to the edge of the screen), escape
codes in the prompt tend to mess things up. You can tell the shell not to
count certain sequences (such as escape codes) by using the
\[...\]
substitution (see below) or by prefixing your prompt with a non-printing
character (such as control-A) followed by a carriage return and then
delimiting the escape codes with this non-printing character. By the way,
don't blame me for this hack; it's in the original
ksh.

The default prompt is the first part of the hostname, followed by
‘$ ’ for non-root users, ‘# ’
for root.

The following backslash-escaped special characters can be used to customise
the prompt:

The default prompt character i.e. ‘#’ if
the effective UID is 0, otherwise ‘$’. Since the shell
interprets ‘$’ as a special character within double
quotes, it is safer in this case to escape the backslash than to try
quoting it.

Used to prefix commands that are printed during execution
tracing (see the set-x command below). Parameter, command, and
arithmetic substitutions are performed before it is printed. The default
is ‘+ ’.

A random number generator. Every time
RANDOM is referenced, it is assigned
the next random number in the range 0-32767. By default,
arc4random(3) is used to
produce values. If the variable RANDOM
is assigned a value, the value is used as the seed to
srand_deterministic(3)
and subsequent references of RANDOM
produce a predictable sequence.

If set to a positive integer in an interactive shell, it
specifies the maximum number of seconds the shell will wait for input
after printing the primary prompt
(PS1). If the time is exceeded, the
shell exits.

If set, this parameter controls the command-line editing
mode for interactive shells. If the last component of the path specified
in this parameter contains the string “vi”,
“emacs”, or “gmacs”, the
vi(1), emacs, or gmacs (Gosling
emacs) editing mode is enabled, respectively. See also the
EDITOR parameter, above.

Tilde expansion, which is done in parallel with parameter substitution, is done
on words starting with an unquoted ‘~’.
The characters following the tilde, up to the first
‘/’, if any, are assumed to be a login
name. If the login name is empty, ‘+’,
or ‘-’, the value of the
HOME,
PWD, or
OLDPWD parameter is substituted,
respectively. Otherwise, the password file is searched for the login name, and
the tilde expression is substituted with the user's home directory. If the
login name is not found in the password file or if any quoting or parameter
substitution occurs in the login name, no substitution is performed.

In parameter assignments (such as those preceding a simple-command or those
occurring in the arguments of alias,
export, readonly,
and typeset), tilde expansion is done after any
assignment (i.e. after the equals sign) or after an unquoted colon
(‘:’); login names are also delimited by colons.

The home directory of previously expanded login names are cached and re-used.
The alias -d command may be used to list, change,
and add to this cache (e.g. alias -d
fac=/usr/local/facilities; cd ~fac/bin).

The expressions are expanded to N words, each
of which is the concatenation of prefix,
stri, and
suffix (e.g. “a{c,b{X,Y},d}e”
expands to four words: “ace”, “abXe”,
“abYe”, and “ade”). As noted in the example, brace
expressions can be nested and the resulting words are not sorted. Brace
expressions must contain an unquoted comma (‘,’) for expansion
to occur (e.g. {} and
{foo} are not expanded). Brace expansion is
carried out after parameter substitution and before file name generation.

A file name pattern is a word containing one or more unquoted
‘?’,
‘*’,
‘+’,
‘@’, or
‘!’ characters or “[..]”
sequences. Once brace expansion has been performed, the shell replaces file
name patterns with the sorted names of all the files that match the pattern
(if no files match, the word is left unchanged). The pattern elements have the
following meaning:

?

Matches any single character.

*

Matches any sequence of characters.

[..]

Matches any of the characters inside the brackets. Ranges
of characters can be specified by separating two characters by a
‘-’ (e.g. “[a0-9]”
matches the letter ‘a’ or any digit). In order to represent
itself, a ‘-’ must either be quoted
or the first or last character in the character list. Similarly, a
‘]’ must be quoted or the first
character in the list if it is to represent itself instead of the end of
the list. Also, a ‘!’ appearing at
the start of the list has special meaning (see below), so to represent
itself it must be quoted or appear later in the list.

Within a bracket expression, the name of a
character class enclosed in
‘[:’ and ‘:]’ stands for the list of all
characters belonging to that class. Supported character classes:

Matches any string that does not match one of the
specified patterns. Examples: The pattern
!(foo|bar) matches all strings except
“foo” and “bar”; the pattern
!(*) matches no strings; the pattern
!(?)* matches all strings (think about
it).

Unlike most shells, ksh never matches
‘.’ and ‘..’.

Note that none of the above pattern elements match either a period
(‘.’) at the start of a file name or a slash
(‘/’), even if they are explicitly used in a [..] sequence;
also, the names ‘.’ and ‘..’ are never matched,
even by the pattern ‘.*’.

If the markdirs option is set, any directories that
result from file name generation are marked with a trailing
‘/’.

When a command is executed, its standard input, standard output, and standard
error (file descriptors 0, 1, and 2, respectively) are normally inherited from
the shell. Three exceptions to this are commands in pipelines, for which
standard input and/or standard output are those set up by the pipeline,
asynchronous commands created when job control is disabled, for which standard
input is initially set to be from /dev/null, and
commands for which any of the following redirections have been specified:

Standard output is redirected to
file. If
file does not exist, it is created; if it
does exist, is a regular file, and the
noclobber option is set, an error occurs;
otherwise, the file is truncated. Note that this means the command
cmd < foo > foo will open
foo for reading and then truncate it when
it opens it for writing, before cmd gets
a chance to actually read foo.

After reading the command line containing this kind of
redirection (called a “here document”), the shell copies
lines from the command source into a temporary file until a line matching
marker is read. When the command is
executed, standard input is redirected from the temporary file. If
marker contains no quoted characters, the
contents of the temporary file are processed as if enclosed in double
quotes each time the command is executed, so parameter, command, and
arithmetic substitutions are performed, along with backslash
(‘\’) escapes for ‘$’,
‘`’,
‘\’, and
‘\newline’. If multiple here
documents are used on the same command line, they are saved in order.

Standard input is duplicated from file descriptor
fd. fd
can be a single digit, indicating the number of an existing file
descriptor; the letter ‘p’,
indicating the file descriptor associated with the output of the current
co-process; or the character ‘-’,
indicating standard input is to be closed.

In any of the above redirections, the file descriptor that is redirected (i.e.
standard input or standard output) can be explicitly given by preceding the
redirection with a single digit. Parameter, command, and arithmetic
substitutions, tilde substitutions, and (if the shell is interactive) file
name generation are all performed on the
file,
marker, and
fd arguments of redirections. Note, however,
that the results of any file name generation are only used if a single file is
matched; if multiple files match, the word with the expanded file name
generation characters is used. Note that in restricted shells, redirections
which can create files cannot be used.

For simple-commands, redirections may appear anywhere in the command; for
compound-commands (if statements, etc.), any
redirections must appear at the end. Redirections are processed after
pipelines are created and in the order they are given, so the following will
print an error with a line number prepended to it:

Integer arithmetic expressions can be used with the
let command, inside $((..)) expressions, inside
array references (e.g.
name[expr]),
as numeric arguments to the test command, and as
the value of an assignment to an integer parameter.

Expressions may contain alpha-numeric parameter identifiers, array references,
and integer constants and may be combined with the following C operators
(listed and grouped in increasing order of precedence):

A parameter that is NULL or unset evaluates to 0. Integer constants may be
specified with arbitrary bases using the notation
base#number,
where base is a decimal integer specifying
the base, and number is a number in the
specified base. Additionally, integers may be prefixed with ‘0X’
or ‘0x’ (specifying base 16) or ‘0’ (base 8) in
all forms of arithmetic expressions, except as numeric arguments to the
test command.

The operators are evaluated as follows:

unary +

Result is the argument (included for completeness).

unary -

Negation.

!

Logical NOT; the result is 1 if argument is zero, 0 if
not.

~

Arithmetic (bit-wise) NOT.

++

Increment; must be applied to a parameter (not a literal or
other expression). The parameter is incremented by 1. When used as a
prefix operator, the result is the incremented value of the parameter;
when used as a postfix operator, the result is the original value of the
parameter.

--

Similar to ++, except the
parameter is decremented by 1.

,

Separates two arithmetic expressions; the left-hand side is
evaluated first, then the right. The result is the value of the expression
on the right-hand side.

=

Assignment; the variable on the left is set to the value on
the right.

Assignment operators.
⟨var⟩⟨op⟩=⟨expr⟩
is the same as
⟨var⟩=⟨var⟩⟨op⟩⟨expr⟩,
with any operator precedence in
⟨expr⟩ preserved. For
example, “var1 *= 5 + 3” is the same as specifying
“var1 = var1 * (5 + 3)”.

||

Logical OR; the result is 1 if either argument is non-zero,
0 if not. The right argument is evaluated only if the left argument is
zero.

&&

Logical AND; the result is 1 if both arguments are
non-zero, 0 if not. The right argument is evaluated only if the left
argument is non-zero.

|

Arithmetic (bit-wise) OR.

^

Arithmetic (bit-wise) XOR (exclusive-OR).

&

Arithmetic (bit-wise) AND.

==

Equal; the result is 1 if both arguments are equal, 0 if
not.

!=

Not equal; the result is 0 if both arguments are equal, 1
if not.

<

Less than; the result is 1 if the left argument is less
than the right, 0 if not.

<= >= >

Less than or equal, greater than or equal, greater than.
See <.

<< >>

Shift left (right); the result is the left argument with
its bits shifted left (right) by the amount given in the right
argument.

+ - * /

Addition, subtraction, multiplication, and division.

%

Remainder; the result is the remainder of the division of
the left argument by the right. The sign of the result is unspecified if
either argument is negative.

⟨arg1⟩?⟨arg2⟩:⟨arg3⟩

If ⟨arg1⟩ is
non-zero, the result is
⟨arg2⟩; otherwise the
result is ⟨arg3⟩.

A co-process, which is a pipeline created with the ‘|&’
operator, is an asynchronous process that the shell can both write to (using
print -p) and read from (using
read -p). The input and output of the co-process
can also be manipulated using >&p and
<&p redirections, respectively. Once a
co-process has been started, another can't be started until the co-process
exits, or until the co-process's input has been redirected using an
execn>&p
redirection. If a co-process's input is redirected in this way, the next
co-process to be started will share the output with the first co-process,
unless the output of the initial co-process has been redirected using an
execn<&p
redirection.

Some notes concerning co-processes:

The only way to close the co-process's input (so the
co-process reads an end-of-file) is to redirect the input to a numbered
file descriptor and then close that file descriptor e.g.
exec 3>&p; exec 3>&-.

In order for co-processes to share a common output, the
shell must keep the write portion of the output pipe open. This means that
end-of-file will not be detected until all co-processes sharing the
co-process's output have exited (when they all exit, the shell closes its
copy of the pipe). This can be avoided by redirecting the output to a
numbered file descriptor (as this also causes the shell to close its
copy). Note that this behaviour is slightly different from the original
Korn shell which closes its copy of the write portion of the co-process
output when the most recently started co-process (instead of when all
sharing co-processes) exits.

print
-p will ignore SIGPIPE signals
during writes if the signal is not being trapped or ignored; the same is
true if the co-process input has been duplicated to another file
descriptor and print
-un is used.

Functions are defined using either Korn shell
functionfunction-name syntax or the Bourne/POSIX
shell function-name() syntax (see below for
the difference between the two forms). Functions are like
.-scripts (i.e. scripts sourced using the
‘.’ built-in) in that they are executed in the current
environment. However, unlike .-scripts, shell
arguments (i.e. positional parameters $1, $2, etc.) are never visible inside
them. When the shell is determining the location of a command, functions are
searched after special built-in commands, before regular and non-regular
built-ins, and before the PATH is searched.

An existing function may be deleted using unset-ffunction-name. A list of functions can be
obtained using typeset +f and the function
definitions can be listed using typeset -f. The
autoload command (which is an alias for
typeset -fu) may be used to create undefined
functions: when an undefined function is executed, the shell searches the path
specified in the FPATH parameter for a file
with the same name as the function, which, if found, is read and executed. If
after executing the file the named function is found to be defined, the
function is executed; otherwise, the normal command search is continued (i.e.
the shell searches the regular built-in command table and
PATH). Note that if a command is not found
using PATH, an attempt is made to autoload
a function using FPATH (this is an
undocumented feature of the original Korn shell).

Functions can have two attributes, “trace” and
“export”, which can be set with typeset
-ft and typeset -fx, respectively. When a
traced function is executed, the shell's xtrace
option is turned on for the function's duration; otherwise, the
xtrace option is turned off. The
“export” attribute of functions is currently not used. In the
original Korn shell, exported functions are visible to shell scripts that are
executed.

Since functions are executed in the current shell environment, parameter
assignments made inside functions are visible after the function completes. If
this is not the desired effect, the typeset
command can be used inside a function to create a local parameter. Note that
special parameters (e.g. $$,
$!) can't be scoped in this way.

The exit status of a function is that of the last command executed in the
function. A function can be made to finish immediately using the
return command; this may also be used to
explicitly specify the exit status.

Functions defined with the function reserved word
are treated differently in the following ways from functions defined with the
() notation:

The $0 parameter is set to the name of the function
(Bourne-style functions leave $0 untouched).

OPTIND
is saved/reset and restored on entry and exit from the function so
getopts can be used properly both inside and
outside the function (Bourne-style functions leave
OPTIND untouched, so using
getopts inside a function interferes with
using getopts outside the function).

The shell is intended to be POSIX compliant; however, in some cases, POSIX
behaviour is contrary either to the original Korn shell behaviour or to user
convenience. How the shell behaves in these cases is determined by the state
of the posix option (set
-o posix). If it is on, the POSIX behaviour is followed; otherwise, it is
not. The posix option is set automatically when
the shell starts up if the environment contains the
POSIXLY_CORRECT parameter. The shell can
also be compiled so that it is in POSIX mode by default; however, this is
usually not desirable.

The following is a list of things that are affected by the state of the
posix option:

echo
options. In POSIX mode, -e and
-E are not treated as options, but printed
like other arguments; in non-POSIX mode, these options control the
interpretation of backslash sequences.

fg
exit status. In POSIX mode, the exit status is 0 if no errors occur; in
non-POSIX mode, the exit status is that of the last foregrounded job.

eval
exit status. If eval gets to see an empty
command (i.e. eval `false`), its exit status
in POSIX mode will be 0. In non-POSIX mode, it will be the exit status of
the last command substitution that was done in the processing of the
arguments to eval (or 0 if there were no
command substitutions).

getopts.
In POSIX mode, options must start with a
‘-’; in non-POSIX mode, options can
start with either ‘-’ or
‘+’.

Brace expansion (also known as alternation). In POSIX
mode, brace expansion is disabled; in non-POSIX mode, brace expansion is
enabled. Note that set -o posix (or setting
the POSIXLY_CORRECT parameter)
automatically turns the braceexpand option
off; however, it can be explicitly turned on later.

set
-. In POSIX mode, this does not clear the
verbose or
xtrace options; in non-POSIX mode, it
does.

set
exit status. In POSIX mode, the exit status of
set is 0 if there are no errors; in non-POSIX
mode, the exit status is that of any command substitutions performed in
generating the set command. For example,
set -- `false`; echo $? prints 0 in POSIX
mode, 1 in non-POSIX mode. This construct is used in most shell scripts
that use the old getopt(1)
command.

Alias expansion. In POSIX mode, alias expansion is only
carried out when reading command words; in non-POSIX mode, alias expansion
is carried out on any word following an alias that ended in a space. For
example, the following for loop uses
parameter ‘i’ in POSIX mode and ‘j’ in
non-POSIX mode:

alias a='for ' i='j'
a i in 1 2; do echo i=$i j=$j; done

test.
In POSIX mode, the expression
‘-t’ (preceded by some number
of ‘!’ arguments) is always true as it is a non-zero length
string; in non-POSIX mode, it tests if file descriptor 1 is a
tty(4) (i.e. the
fd argument to the
-t test may be left out and defaults to
1).

After evaluation of command-line arguments, redirections, and parameter
assignments, the type of command is determined: a special built-in, a
function, a regular built-in, or the name of a file to execute found using the
PATH parameter. The checks are made in the
above order. Special built-in commands differ from other commands in that the
PATH parameter is not used to find them, an
error during their execution can cause a non-interactive shell to exit, and
parameter assignments that are specified before the command are kept after the
command completes. Just to confuse things, if the
posix option is turned off (see the
set command below), some special commands are
very special in that no field splitting, file globbing, brace expansion, nor
tilde expansion is performed on arguments that look like assignments. Regular
built-in commands are different only in that the
PATH parameter is not used to find them.

The original ksh and POSIX differ somewhat in which
commands are considered special or regular:

Execute the commands in
file in the current environment. The file
is searched for in the directories of
PATH. If arguments are given, the
positional parameters may be used to access them while
file is being executed. If no arguments
are given, the positional parameters are those of the environment the
command is used in.

Without arguments, alias lists
all aliases. For any name without a value, the existing alias is listed.
Any name with a value defines an alias (see
Aliases above).

When listing aliases, one of two formats is used. Normally, aliases are
listed as
name=value,
where value is quoted. If options were
preceded with ‘+’, or a lone
‘+’ is given on the command line,
only name is printed.

The -d option causes directory aliases, which
are used in tilde expansion, to be listed or set (see
Tilde expansion
above).

If the -p option is used, each alias is
prefixed with the string “alias ”.

The -t option indicates that tracked aliases
are to be listed/set (values specified on the command line are ignored for
tracked aliases). The -r option indicates
that all tracked aliases are to be reset.

The -x option sets
(+xclears) the
export attribute of an alias or, if no names are given, lists the aliases
with the export attribute (exporting an alias has no effect).

In
Emacs editing
mode, the specified editing command is bound to the given
string. Future input of the
string will cause the editing command to
be immediately invoked. Bindings have no effect in
Vi editing mode.

If the -m flag is given, the specified input
string will afterwards be immediately
replaced by the given substitute string,
which may contain editing commands. Control characters may be written
using caret notation. For example, ^X represents Control-X.

If a certain character occurs as the first character of any bound
multi-character string sequence, that
character becomes a command prefix character. Any character sequence that
starts with a command prefix character but that is not bound to a command
or substitute is implicitly considered as bound to the
‘error’ command. By default, two command prefix characters
exist: Escape (^[) and Control-X (^X).

The following default bindings show how the arrow keys on an ANSI terminal
or xterm are bound (of course some escape sequences won't work out quite
this nicely):

Set the working directory to
dir. If the parameter
CDPATH is set, it lists the search path
for the directory containing dir. A
NULL path means the current directory.
If dir is found in any component of the
CDPATH search path other than the
NULL path, the name of the new working
directory will be written to standard output. If
dir is missing, the home directory
HOME is used. If
dir is
‘-’, the previous working directory
is used (see the OLDPWD parameter).

If the -L option (logical path) is used or if
the physical option isn't set (see the
set command below), references to
‘..’ in dir are relative to
the path used to get to the directory. If the
-P option (physical path) is used or if the
physical option is set, ‘..’ is
relative to the filesystem directory tree. The
PWD and
OLDPWD parameters are updated to
reflect the current and old working directory, respectively.

If neither the -v nor
-V option is given,
cmd is executed exactly as if
command had not been specified, with two
exceptions: firstly, cmd cannot be an
alias or a shell function; and secondly, special built-in commands lose
their specialness (i.e. redirection and utility errors do not cause the
shell to exit, and command assignments are not permanent).

If the -p option is given, a default search
path is used instead of the current value of
PATH (the actual value of the default
path is system dependent: on POSIX-ish systems, it is the value returned
by getconf PATH). Nevertheless, reserved
words, aliases, shell functions, and builtin commands are still found
before external commands.

If the -v option is given, instead of executing
cmd, information about what would be
executed is given (and the same is done for arg
...). For special and regular built-in commands and functions, their
names are simply printed; for aliases, a command that defines them is
printed; and for commands found by searching the
PATH parameter, the full path of the
command is printed. If no command is found (i.e. the path search fails),
nothing is printed and command exits with a
non-zero status. The -V option is like the
-v option, except it is more verbose.

Prints its arguments (separated by spaces) followed by a
newline, to the standard output. The newline is suppressed if any of the
arguments contain the backslash sequence
‘\c’. See the
print command below for a list of other
backslash sequences that are recognized.

The options are provided for compatibility with BSD
shell scripts. The -n option suppresses the
trailing newline, -e enables backslash
interpretation (a no-op, since this is normally done), and
-E suppresses backslash interpretation. If
the posix option is set, only the first
argument is treated as an option, and only if it is exactly
“-n”.

If no command is given except for I/O redirection, the I/O redirection is
permanent and the shell is not replaced. Any file descriptors greater than
2 which are opened or dup(2)'d
in this way are not made available to other executed commands (i.e.
commands that are not built-in to the shell). Note that the Bourne shell
differs here; it does pass these file descriptors on.

Sets the export attribute of the named parameters. Exported
parameters are passed in the environment to executed commands. If values
are specified, the named parameters are also assigned.

If no parameters are specified, the names of all parameters with the export
attribute are printed one per line, unless the
-p option is used, in which case
export commands defining all exported
parameters, including their values, are printed.

Fix command. first and
last select commands from the history.
Commands can be selected by history number or a string specifying the most
recent command starting with that string. The
-l option lists the command on standard
output, and -n inhibits the default command
numbers. The -r option reverses the order of
the list. Without -l, the selected commands
are edited by the editor specified with the
-e option, or if no
-e is specified, the editor specified by the
FCEDIT parameter (if this parameter is
not set, /bin/ed is used), and then executed
by the shell.

Re-execute the most recent command beginning with
prefix, or the previous command if no
prefix is specified, performing the
optional substitution of old with
new. If -g
is specified, all occurrences of old are
replaced with new. The editor is not
invoked when the -s flag is used. The
obsolescent equivalent “-e-” is also accepted. This command is
usually accessed with the predefined alias r='fc
-s'.

Used by shell procedures to parse the specified arguments
(or positional parameters, if no arguments are given) and to check for
legal options. optstring contains the
option letters that getopts is to recognize.
If a letter is followed by a colon, the option is expected to have an
argument. Options that do not take arguments may be grouped in a single
argument. If an option takes an argument and the option character is not
the last character of the argument it is found in, the remainder of the
argument is taken to be the option's argument; otherwise, the next
argument is the option's argument.

Each time getopts is invoked, it places the
next option in the shell parameter name
and the index of the argument to be processed by the next call to
getopts in the shell parameter
OPTIND. If the option was introduced
with a ‘+’, the option placed in
name is prefixed with a
‘+’. When an option requires an
argument, getopts places it in the shell
parameter OPTARG.

When an illegal option or a missing option argument is encountered, a
question mark or a colon is placed in
name (indicating an illegal option or
missing argument, respectively) and
OPTARG is set to the option character
that caused the problem. Furthermore, if
optstring does not begin with a colon, a
question mark is placed in name,
OPTARG is unset, and an error message
is printed to standard error.

When the end of the options is encountered,
getopts exits with a non-zero exit status.
Options end at the first (non-option argument) argument that does not
start with a ‘-’, or when a
‘--’ argument is encountered.

Option parsing can be reset by setting
OPTIND to 1 (this is done automatically
whenever the shell or a shell procedure is invoked).

Warning: Changing the value of the shell parameter
OPTIND to a value other than 1, or
parsing different sets of arguments without resetting
OPTIND, may lead to unexpected results.

Without arguments, any hashed executable command pathnames
are listed. The -r option causes all hashed
commands to be removed from the hash table. Each
name is searched as if it were a command
name and added to the hash table if it is an executable command.

Display information about the specified job(s); if no jobs
are specified, all jobs are displayed. The -n
option causes information to be displayed only for jobs that have changed
state since the last notification. If the -l
option is used, the process ID of each process in a job is also listed.
The -p option causes only the process group
of each job to be printed. See
Job control below for the
format of job and the displayed job.

Send the specified signal to the specified jobs, process
IDs, or process groups. If no signal is specified, the
TERM signal is sent. If a job is
specified, the signal is sent to the job's process group. See
Job control below for the
format of job.

Each expression is evaluated (see
Arithmetic
expressions above). If all expressions are successfully evaluated, the
exit status is 0 (1) if the last expression evaluated to non-zero (zero).
If an error occurs during the parsing or evaluation of an expression, the
exit status is greater than 1. Since expressions may need to be quoted,
((expr)) is syntactic sugar for let
"expr".

print
prints its arguments on the standard output, separated by spaces and
terminated with a newline. The -n option
suppresses the newline. By default, certain C escapes are translated.
These include ‘\b’,
‘\f’,
‘\n’,
‘\r’,
‘\t’,
‘\v’, and
‘\0###’
(‘#’ is an octal digit, of which
there may be 0 to 3). ‘\c’ is
equivalent to using the -n option.
‘\’ expansion may be inhibited with
the -r option. The
-s option prints to the history file instead
of standard output; the -u option prints to
file descriptor n
(n defaults to 1 if omitted); and the
-p option prints to the co-process (see
Co-processes above).

The -R option is used to emulate, to some
degree, the BSDecho(1) command, which does
not process ‘\’ sequences unless the
-e option is given. As above, the
-n option suppresses the trailing newline.

Print the present working directory. If the
-L option is used or if the
physical option isn't set (see the
set command below), the logical path is
printed (i.e. the path used to cd to the
current directory). If the -P option
(physical path) is used or if the physical
option is set, the path determined from the filesystem (by following
‘..’ directories to the root directory) is printed.

Reads a line of input from the standard input, separates
the line into fields using the IFS
parameter (see
Substitution above), and
assigns each field to the specified parameters. If there are more
parameters than fields, the extra parameters are set to
NULL, or alternatively, if there are
more fields than parameters, the last parameter is assigned the remaining
fields (inclusive of any separating spaces). If no parameters are
specified, the REPLY parameter is used.
If the input line ends in a backslash and the
-r option was not used, the backslash and the
newline are stripped and more input is read. If no input is read,
read exits with a non-zero status.

The first parameter may have a question mark and a string appended to it, in
which case the string is used as a prompt (printed to standard error
before any input is read) if the input is a
tty(4) (e.g.
read nfoo?'number of foos: ').

The -un and
-p options cause input to be read from file
descriptor n
(n defaults to 0 if omitted) or the
current co-process (see
Co-processes above for
comments on this), respectively. If the -s
option is used, input is saved to the history file.

Sets the read-only attribute of the named parameters. If
values are given, parameters are set to them before setting the attribute.
Once a parameter is made read-only, it cannot be unset and its value
cannot be changed.

If no parameters are specified, the names of all parameters with the
read-only attribute are printed one per line, unless the
-p option is used, in which case
readonly commands defining all read-only
parameters, including their values, are printed.

Returns from a function or .
script, with exit status status. If no
status is given, the exit status of the
last executed command is used. If used outside of a function or
. script, it has the same effect as
exit. Note that
ksh treats both profile and
ENV files as
. scripts, while the original Korn shell only
treats profiles as . scripts.

The set command can be used to
set (-) or clear
(+) shell options, set the positional
parameters, or set an array parameter. Options can be changed using the
+-ooption
syntax, where option is the long name of
an option, or using the
+-letter
syntax, where letter is the option's
single letter name (not all options have a single letter name). The
following table lists both option letters (if they exist) and long names
along with a description of what the option does:

Sets the elements of the array parameter
name to
arg ... If
-A is used, the array is reset (i.e.
emptied) first; if +A is used, the first
N elements are set (where N is the number of arguments); the rest are
left untouched.

Exit (after executing the
ERR trap) as soon as an error
occurs or a command fails (i.e. exits with a non-zero status). This
does not apply to commands whose exit status is explicitly tested by a
shell construct such as if,
until,
while, or !
statements. For && or
||, only the status of the last command
is tested.

The shell is a privileged shell. It is set
automatically if, when the shell starts, the real UID or GID does not
match the effective UID (EUID) or GID (EGID), respectively. See above
for a description of what this means.

Do not kill running jobs with a
SIGHUP signal when a login shell
exits. Currently set by default; this is different from the original
Korn shell (which doesn't have this option, but does send the
SIGHUP signal).

Causes the cd and
pwd commands to use
“physical” (i.e. the filesystem's) ‘..’
directories instead of “logical” directories (i.e. the
shell handles ‘..’, which allows the user to be
oblivious of symbolic links to directories). Clear by default. Note
that setting this option does not affect the current value of the
PWD parameter; only the
cd command changes
PWD. See the
cd and pwd
commands above for more details.

No effect. In the original Korn shell, unless
viraw was set, the vi command-line mode
would let the tty(4) driver
do the work until ESC (^[) was entered.
ksh is always in viraw mode.

These options can also be used upon invocation of the shell. The current set
of options (with single letter names) can be found in the parameter
‘$-’. set-o with no option name will list all the
options and whether each is on or off; set +o
will print the current shell options in a form that can be reinput to the
shell to achieve the same option settings.

Remaining arguments, if any, are positional parameters and are assigned, in
order, to the positional parameters (i.e. $1, $2, etc.). If options end
with ‘--’ and there are no remaining
arguments, all positional parameters are cleared. If no options or
arguments are given, the values of all names are printed. For unknown
historical reasons, a lone ‘-’
option is treated specially - it clears both the
-x and -v
options.

Stops the shell as if it had received the suspend character
from the terminal. It is not possible to suspend a login shell unless the
parent process is a member of the same terminal session but is a member of
a different process group. As a general rule, if the shell was started by
another shell or via su(1), it
can be suspended.

test
evaluates the expression and returns zero
status if true, 1 if false, or greater than 1 if there was an error. It is
normally used as the condition command of if
and while statements. Symbolic links are
followed for all file expressions except
-h and -L.

Shell option is set
(see the set command above for a list of
options). As a non-standard extension, if the option starts with a
‘!’, the test is negated; the
test always fails if option doesn't
exist (so [ -o foo -o -o !foo ] returns true if and only if option
foo exists).

On operating systems not supporting
/dev/fd/n
devices (where n is a file descriptor
number), the test command will attempt to
fake it for all tests that operate on files (except the
-e test). For example, [ -w /dev/fd/2 ] tests
if file descriptor 2 is writable.

Note that some special rules are applied (courtesy of POSIX) if the number
of arguments to test or
[ ... ] is less than five: if leading
‘!’ arguments can be stripped such
that only one argument remains then a string length test is performed
(again, even if the argument is a unary operator); if leading
‘!’ arguments can be stripped such
that three arguments remain and the second argument is a binary operator,
then the binary operation is performed (even if the first argument is a
unary operator, including an unstripped
‘!’).

Note: A common mistake is to use “if [
$foo = bar ]” which fails if parameter “foo” is
NULL or unset, if it has embedded
spaces (i.e. IFS characters), or if it
is a unary operator like ‘!’ or
‘-n’. Use tests like “if
[ "X$foo" = Xbar ]” instead.

If a pipeline is given,
the times used to execute the pipeline are reported. If no pipeline is
given, then the user and system time used by the shell itself, and all the
commands it has run since it was started, are reported. The times reported
are the real time (elapsed time from start to finish), the user CPU time
(time spent running in user mode), and the system CPU time (time spent
running in kernel mode). Times are reported to standard error; the format
of the output is:

0m0.00s real 0m0.00s user 0m0.00s
system

If the -p option is given the output is
slightly longer:

real 0.00
user 0.00
sys 0.00

It is an error to specify the -p option unless
pipeline is a simple command.

Simple redirections of standard error do not affect the output of the
time command:

$ time sleep 1 2> afile

$ { time sleep 1; } 2>
afile

Times for the first command do not go to “afile”, but those of
the second command do.

Sets a trap handler that is to be executed when any of the
specified signals are received. handler
is either a NULL string, indicating the
signals are to be ignored, a minus sign (‘-’), indicating
that the default action is to be taken for the signals (see
signal(3)), or a string
containing shell commands to be evaluated and executed at the first
opportunity (i.e. when the current command completes, or before printing
the next PS1 prompt) after receipt of
one of the signals. signal is the name of
a signal (e.g. PIPE or
ALRM) or the number of the signal (see
the kill -l command above).

There are two special signals: EXIT (also
known as 0), which is executed when the shell is about to exit, and
ERR, which is executed after an error
occurs (an error is something that would cause the shell to exit if the
-e or errexit
option were set - see the set command above).
EXIT handlers are executed in the
environment of the last executed command. Note that for non-interactive
shells, the trap handler cannot be changed for signals that were ignored
when the shell started.

With no arguments, trap lists, as a series of
trap commands, the current state of the traps
that have been set since the shell started. Note that the output of
trap cannot be usefully piped to another
process (an artifact of the fact that traps are cleared when subprocesses
are created).

The original Korn shell's DEBUG trap and
the handling of ERR and
EXIT traps in functions are not yet
implemented.

Display or set parameter attributes. With no
name arguments, parameter attributes are
displayed; if no options are used, the current attributes of all
parameters are printed as typeset commands;
if an option is given (or ‘-’ with
no option letter), all parameters and their values with the specified
attributes are printed; if options are introduced with
‘+’, parameter values are not
printed.

If name arguments are given, the attributes
of the named parameters are set (-) or
cleared (+). Values for parameters may
optionally be specified. If typeset is used
inside a function, any newly created parameters are local to the function.

When -f is used,
typeset operates on the attributes of
functions. As with parameters, if no name
arguments are given, functions are listed with their values (i.e.
definitions) unless options are introduced with
‘+’, in which case only the function
names are reported.

Integer attribute. n
specifies the base to use when displaying the integer (if not
specified, the base given in the first assignment is used). Parameters
with this attribute may be assigned values containing arithmetic
expressions.

Left justify attribute.
n specifies the field width. If
n is not specified, the current width
of a parameter (or the width of its first assigned value) is used.
Leading whitespace (and zeros, if used with the
-Z option) is stripped. If necessary,
values are either truncated or space padded to fit the field
width.

Right justify attribute.
n specifies the field width. If
n is not specified, the current width
of a parameter (or the width of its first assigned value) is used.
Trailing whitespace is stripped. If necessary, values are either
stripped of leading characters or space padded to make them fit the
field width.

Upper case attribute. All lower case characters in
values are converted to upper case. (In the original Korn shell, this
parameter meant “unsigned integer” when used with the
-i option, which meant upper case letters
would never be used for bases greater than 10. See the
-U option.)

For functions, -u is the undefined
attribute. See
Functions above for the
implications of this.

Display or set process limits. If no options are used, the
file size limit (-f) is assumed.
value, if specified, may be either an
arithmetic expression starting with a number or the word
“unlimited”. The limits affect the shell and any processes
created by the shell after a limit is imposed; limits may not be increased
once they are set.

Display or set the file permission creation mask, or umask
(see umask(2)). If the
-S option is used, the mask displayed or set
is symbolic; otherwise, it is an octal number.

Symbolic masks are like those used by
chmod(1). When used, they
describe what permissions may be made available (as opposed to octal masks
in which a set bit means the corresponding bit is to be cleared). For
example, “ug=rwx,o=” sets the mask so files will not be
readable, writable, or executable by “others”, and is
equivalent (on most systems) to the octal mask “007”.

The aliases for the given names are removed. If the
-a option is used, all aliases are removed.
If the -t or -d
options are used, the indicated operations are carried out on tracked or
directory aliases, respectively.

Wait for the specified job(s) to finish. The exit status of
wait is that of the last specified job; if
the last job is killed by a signal, the exit status is 128 + the number of
the signal (see kill -lexit-status above); if the last specified
job can't be found (because it never existed, or had already finished),
the exit status of wait is 127. See
Job control below for the
format of job.
wait will return if a signal for which a trap
has been set is received, or if a
SIGHUP,
SIGINT, or
SIGQUIT signal is received.

If no jobs are specified, wait waits for all
currently running jobs (if any) to finish and exits with a zero status. If
job monitoring is enabled, the completion status of jobs is printed (this
is not the case when jobs are explicitly specified).

For each name, the type of
command is listed (reserved word, built-in, alias, function, tracked
alias, or executable). If the -p option is
used, a path search is performed even if
name is a reserved word, alias, etc.
Without the -v option,
whence is similar to
command-v
except that whence won't print aliases as
alias commands. With the -v option,
whence is the same as
command-V. Note
that for whence, the
-p option does not affect the search path
used, as it does for command. If the type of
one or more of the names could not be determined, the exit status is
non-zero.

Job control refers to the shell's ability to monitor and control jobs, which are
processes or groups of processes created for commands or pipelines. At a
minimum, the shell keeps track of the status of the background (i.e.
asynchronous) jobs that currently exist; this information can be displayed
using the jobs commands. If job control is fully
enabled (using set -m or
set -o monitor), as it is for interactive shells,
the processes of a job are placed in their own process group. Foreground jobs
can be stopped by typing the suspend character from the terminal (normally
^Z), jobs can be restarted in either the foreground or background using the
fg and bg commands,
and the state of the terminal is saved or restored when a foreground job is
stopped or restarted, respectively.

When a job is created, it is assigned a job number. For interactive shells, this
number is printed inside “[..]”, followed by the process IDs of
the processes in the job when an asynchronous command is run. A job may be
referred to in the bg,
fg, jobs,
kill, and wait
commands either by the process ID of the last process in the command pipeline
(as stored in the $! parameter) or by prefixing
the job number with a percent sign (‘%’). Other percent
sequences can also be used to refer to jobs:

%+ | %% | %

The most recently stopped job or, if there are no stopped
jobs, the oldest running job.

%-

The job that would be the %+
job if the latter did not exist.

%n

The job with job number
n.

%?string

The job with its command containing the string
string (an error occurs if multiple jobs
are matched).

%string

The job with its command starting with the string
string (an error occurs if multiple jobs
are matched).

When a job changes state (e.g. a background job finishes or foreground job is
stopped), the shell prints the following status information:

[number]
flag status command

where...

number

is the job number of the job;

flag

is the ‘+’ or
‘-’ character if the job is the
%+ or %- job,
respectively, or space if it is neither;

status

indicates the current state of the job and can be:

Done
[number]

The job exited. number
is the exit status of the job, which is omitted if the status is
zero.

Running

The job has neither stopped nor exited (note that
running does not necessarily mean consuming CPU time - the process
could be blocked waiting for some event).

Stopped
[signal]

The job was stopped by the indicated
signal (if no signal is given, the
job was stopped by SIGTSTP).

signal-description
[“core dumped”]

The job was killed by a signal (e.g. memory fault,
hangup); use kill -l for a list of signal
descriptions. The “core dumped” message indicates the
process created a core file.

command

is the command that created the process. If there are
multiple processes in the job, each process will have a line showing its
command and possibly its
status, if it is different from the
status of the previous process.

When an attempt is made to exit the shell while there are jobs in the stopped
state, the shell warns the user that there are stopped jobs and does not exit.
If another attempt is immediately made to exit the shell, the stopped jobs are
sent a SIGHUP signal and the shell exits.
Similarly, if the nohup option is not set and
there are running jobs when an attempt is made to exit a login shell, the
shell warns the user and does not exit. If another attempt is immediately made
to exit the shell, the running jobs are sent a
SIGHUP signal and the shell exits.

The shell supports three modes of reading command lines from a
tty(4) in an interactive session,
controlled by the emacs,
gmacs, and vi
options (at most one of these can be set at once). The default is
emacs. Editing modes can be set explicitly using
the set built-in, or implicitly via the
EDITOR and
VISUAL environment variables. If none of
these options are enabled, the shell simply reads lines using the normal
tty(4) driver. If the
emacs or gmacs
option is set, the shell allows emacs-like editing of the command; similarly,
if the vi option is set, the shell allows vi-like
editing of the command. These modes are described in detail in the following
sections.

In these editing modes, if a line is longer than the screen width (see the
COLUMNS parameter), a
‘>’,
‘+’, or
‘<’ character is displayed in the
last column indicating that there are more characters after, before and after,
or before the current position, respectively. The line is scrolled
horizontally as necessary.

When the emacs option is set, interactive input
line editing is enabled. Warning: This mode is slightly different from the
emacs mode in the original Korn shell. In this mode, various editing commands
(typically bound to one or more control characters) cause immediate actions
without waiting for a newline. Several editing commands are bound to
particular control characters when the shell is invoked; these bindings can be
changed using the bind command.

The following is a list of available editing commands. Each description starts
with the name of the command, suffixed with a colon; an
[n] (if the command
can be prefixed with a count); and any keys the command is bound to by
default, written using caret notation e.g. the ASCII ESC character is written
as ^[. ^[A-Z] sequences are not case sensitive. A count prefix for a command
is entered using the sequence ^[n, where
n is a sequence of 1 or more digits. Unless
otherwise specified, if a count is omitted, it defaults to 1.

Note that editing command names are used only with the
bind command. Furthermore, many editing commands
are useful only on terminals with a visible cursor. The default bindings were
chosen to resemble corresponding Emacs key bindings. The user's
tty(4) characters (e.g.
ERASE) are bound to reasonable substitutes
and override the default bindings.

abort: ^C, ^G

Useful as a response to a request for a
search-history pattern in order to abort the
search.

auto-insert:
[n]

Simply causes the character to appear as literal input.
Most ordinary characters are bound to this.

backward-char:
[n]
^B, ^X^D

Moves the cursor backward
n characters.

backward-word:
[n]
^[b

Moves the cursor backward to the beginning of the word;
words consist of alphanumerics, underscore (‘_’), and dollar
sign (‘$’) characters.

beginning-of-history: ^[<

Moves to the beginning of the history.

beginning-of-line: ^A

Moves the cursor to the beginning of the edited input
line.

capitalize-word:
[n]
^[C, ^[c

Uppercase the first character in the next
n words, leaving the cursor past the end
of the last word.

comment: ^[#

If the current line does not begin with a comment
character, one is added at the beginning of the line and the line is
entered (as if return had been pressed); otherwise, the existing comment
characters are removed and the cursor is placed at the beginning of the
line.

complete: ^[^[

Automatically completes as much as is unique of the command
name or the file name containing the cursor. If the entire remaining
command or file name is unique, a space is printed after its completion,
unless it is a directory name in which case
‘/’ is appended. If there is no
command or file name with the current partial word as its prefix, a bell
character is output (usually causing a beep to be sounded).

Custom completions may be configured by creating an array named
‘complete_command’, optionally
suffixed with an argument number to complete only for a single argument.
So defining an array named
‘complete_kill’ provides possible
completions for any argument to the
kill(1) command, but
‘complete_kill_1’ only completes the
first argument. For example, the following command makes
ksh offer a selection of signal names for the
first argument to kill(1):

set -A complete_kill_1 -- -9 -HUP -INFO
-KILL -TERM

complete-command: ^X^[

Automatically completes as much as is unique of the command
name having the partial word up to the cursor as its prefix, as in the
complete command above.

complete-file: ^[^X

Automatically completes as much as is unique of the file
name having the partial word up to the cursor as its prefix, as in the
complete command described above.

complete-list: ^I, ^[=

Complete as much as is possible of the current word, and
list the possible completions for it. If only one completion is possible,
match as in the complete command above.

delete-char-backward:
[n]
ERASE, ^?,
^H

Deletes n characters
before the cursor.

delete-char-forward:
[n]
Delete

Deletes n characters after
the cursor.

delete-word-backward:
[n]
WERASE, ^[ERASE,
^W, ^[^?, ^[^H,
^[h

Deletes n words before the
cursor.

delete-word-forward:
[n]
^[d

Deletes n words after the
cursor.

down-history:
[n]
^N, ^XB

Scrolls the history buffer forward
n lines (later). Each input line
originally starts just after the last entry in the history buffer, so
down-history is not useful until either
search-history or
up-history has been performed.

downcase-word:
[n]
^[L, ^[l

Lowercases the next n
words.

end-of-history: ^[>

Moves to the end of the history.

end-of-line: ^E

Moves the cursor to the end of the input line.

eot: ^_

Acts as an end-of-file; this is useful because edit-mode
input disables normal terminal input canonicalization.

eot-or-delete:
[n]
^D

Acts as eot if alone on a
line; otherwise acts as
delete-char-forward.

error:

Error (ring the bell).

exchange-point-and-mark: ^X^X

Places the cursor where the mark is and sets the mark to
where the cursor was.

expand-file: ^[*

Appends a ‘*’ to the
current word and replaces the word with the result of performing file
globbing on the word. If no files match the pattern, the bell is
rung.

forward-char:
[n]
^F, ^XC

Moves the cursor forward n
characters.

forward-word:
[n]
^[f

Moves the cursor forward to the end of the
nth word.

goto-history:
[n]
^[g

Goes to history number
n.

kill-line: KILL

Deletes the entire input line.

kill-to-eol:
[n]
^K

Deletes the input from the cursor to the end of the line if
n is not specified; otherwise deletes
characters between the cursor and column
n.

list: ^[?

Prints a sorted, columnated list of command names or file
names (if any) that can complete the partial word containing the cursor.
Directory names have ‘/’ appended to
them.

list-command: ^X?

Prints a sorted, columnated list of command names (if any)
that can complete the partial word containing the cursor.

list-file: ^X^Y

Prints a sorted, columnated list of file names (if any)
that can complete the partial word containing the cursor. File type
indicators are appended as described under
list above.

newline: ^J, ^M

Causes the current input line to be processed by the shell.
The current cursor position may be anywhere on the line.

newline-and-next: ^O

Causes the current input line to be processed by the shell,
and the next line from history becomes the current line. This is only
useful after an up-history or
search-history.

no-op: QUIT

This does nothing.

prev-hist-word:
[n]
^[., ^[_

The last (nth) word of the
previous command is inserted at the cursor.

quote: ^^

The following character is taken literally rather than as
an editing command.

redraw: ^L

Reprints the prompt string and the current input line.

search-character-backward:
[n]
^[^]

Search backward in the current line for the
nth occurrence of the next character
typed.

search-character-forward:
[n]
^]

Search forward in the current line for the
nth occurrence of the next character
typed.

search-history: ^R

Enter incremental search mode. The internal history list is
searched backwards for commands matching the input. An initial
‘^’ in the search string anchors the
search. The abort key will leave search mode. Other commands will be
executed after leaving search mode. Successive
search-history commands continue searching
backward to the next previous occurrence of the pattern. The history
buffer retains only a finite number of lines; the oldest are discarded as
necessary.

set-mark-command: ^[⟨space⟩

Set the mark at the cursor position.

transpose-chars: ^T

If at the end of line, or if the
gmacs option is set, this exchanges the two
previous characters; otherwise, it exchanges the previous and current
characters and moves the cursor one character to the right.

up-history:
[n]
^P, ^XA

Scrolls the history buffer backward
n lines (earlier).

upcase-word:
[n]
^[U, ^[u

Uppercase the next n
words.

quote: ^V

Synonym for ^^.

yank: ^Y

Inserts the most recently killed text string at the current
cursor position.

yank-pop: ^[y

Immediately after a yank,
replaces the inserted text string with the next previously killed text
string.

The following editing commands lack default bindings but can be used with the
bind command:

The _ command is different
(in ksh it is the last argument command; in
vi(1) it goes to the start of
the current line).

The / and
G commands move in the opposite direction to
the j command.

Commands which don't make sense in a single line editor
are not available (e.g. screen movement commands and
ex(1)-style colon
(:) commands).

Note that the ^X stands for control-X; also ⟨esc⟩,
⟨space⟩, and ⟨tab⟩ are used for escape, space, and
tab, respectively (no kidding).

Like vi(1), there are two modes:
“insert” mode and “command” mode. In insert mode,
most characters are simply put in the buffer at the current cursor position as
they are typed; however, some characters are treated specially. In particular,
the following characters are taken from current
tty(4) settings (see
stty(1)) and have their usual
meaning (normal values are in parentheses): kill (^U), erase (^?), werase
(^W), eof (^D), intr (^C), and quit (^\). In addition to the above, the
following characters are also treated specially in insert mode:

^E

Command and file name enumeration (see below).

^F

Command and file name completion (see below). If used twice
in a row, the list of possible completions is displayed; if used a third
time, the completion is undone.

^H

Erases previous character.

^J | ^M

End of line. The current line is read, parsed, and executed
by the shell.

^V

Literal next. The next character typed is not treated
specially (can be used to insert the characters being described
here).

In command mode, each character is interpreted as a command. Characters that
don't correspond to commands, are illegal combinations of commands, or are
commands that can't be carried out, all cause beeps. In the following command
descriptions, an [n]
indicates the command may be prefixed by a number (e.g.
10l moves right 10 characters); if no number
prefix is used, n is assumed to be 1 unless
otherwise specified. The term “current position” refers to the
position between the cursor and the character preceding the cursor. A
“word” is a sequence of letters, digits, and underscore
characters or a sequence of non-letter, non-digit, non-underscore, and
non-whitespace characters (e.g. “ab2*&^” contains two words)
and a “big-word” is a sequence of non-whitespace characters.

Special ksh vi commands:

The following commands are not in, or are different from, the normal vi file
editor:

[n]_

Insert a space followed by the
nth big-word from the last command in the
history at the current position and enter insert mode; if
n is not specified, the last word is
inserted.

#

Insert the comment character (‘#’) at the
start of the current line and return the line to the shell (equivalent to
I#^J).

[n]g

Like G, except if
n is not specified, it goes to the most
recent remembered line.

[n]v

Edit line n using the
vi(1) editor; if
n is not specified, the current line is
edited. The actual command executed is fc -e
${VISUAL:-${EDITOR:-vi}}n.

* and ^X

Command or file name expansion is applied to the current
big-word (with an appended ‘*’ if
the word contains no file globbing characters) - the big-word is replaced
with the resulting words. If the current big-word is the first on the line
or follows one of the characters
‘;’,
‘|’,
‘&’,
‘(’, or
‘)’, and does not contain a slash
(‘/’), then command expansion is done; otherwise file name
expansion is done. Command expansion will match the big-word against all
aliases, functions, and built-in commands as well as any executable files
found by searching the directories in the
PATH parameter. File name expansion
matches the big-word against the files in the current directory. After
expansion, the cursor is placed just past the last word and the editor is
in insert mode.

[n]\,
[n]^F,
[n]⟨tab⟩,
and
[n]⟨esc⟩

Command/file name completion. Replace the current big-word
with the longest unique match obtained after performing command and file
name expansion. ⟨tab⟩ is only recognized if the
vi-tabcomplete option is set, while
⟨esc⟩ is only recognized if the
vi-esccomplete option is set (see
set -o). If
n is specified, the
nth possible completion is selected (as
reported by the command/file name enumeration command).

= and ^E

Command/file name enumeration. List all the commands or
files that match the current big-word.

@c

Macro expansion. Execute the commands found in the alias
_c.

Intra-line movement commands:

[n]h
and [n]^H

Move left n
characters.

[n]l
and
[n]⟨space⟩

Move right n
characters.

0

Move to column 0.

^

Move to the first non-whitespace character.

[n]|

Move to column n.

$

Move to the last character.

[n]b

Move back n words.

[n]B

Move back n
big-words.

[n]e

Move forward to the end of the word,
n times.

[n]E

Move forward to the end of the big-word,
n times.

[n]w

Move forward n words.

[n]W

Move forward n
big-words.

%

Find match. The editor looks forward for the nearest
parenthesis, bracket, or brace and then moves the cursor to the matching
parenthesis, bracket, or brace.

[n]fc

Move forward to the nth
occurrence of the character c.

[n]Fc

Move backward to the nth
occurrence of the character c.

[n]tc

Move forward to just before the
nth occurrence of the character
c.

[n]Tc

Move backward to just before the
nth occurrence of the character
c.

[n];

Repeats the last f,
F, t, or
T command.

[n],

Repeats the last f,
F, t, or
T command, but moves in the opposite
direction.

Inter-line movement commands:

[n]j,
[n]+,
and
[n]^N

Move to the nth next line
in the history.

[n]k,
[n]-,
and
[n]^P

Move to the nth previous
line in the history.

[n]G

Move to line n in the
history; if n is not specified, the
number of the first remembered line is used.

[n]g

Like G, except if
n is not specified, it goes to the most
recent remembered line.

[n]/string

Search backward through the history for the
nth line containing
string; if
string starts with
‘^’, the remainder of the string
must appear at the start of the history line for it to match.

[n]?string

Same as /, except it searches
forward through the history.

[n]n

Search for the nth
occurrence of the last search string; the direction of the search is the
same as the last search.

[n]N

Search for the nth
occurrence of the last search string; the direction of the search is the
opposite of the last search.

Edit commands

[n]a

Append text n times; goes
into insert mode just after the current position. The append is only
replicated if command mode is re-entered i.e. ⟨esc⟩ is
used.

[n]A

Same as a, except it appends
at the end of the line.

[n]i

Insert text n times; goes
into insert mode at the current position. The insertion is only replicated
if command mode is re-entered i.e. ⟨esc⟩ is used.

[n]I

Same as i, except the
insertion is done just before the first non-blank character.

[n]s

Substitute the next n
characters (i.e. delete the characters and go into insert mode).

S

Substitute whole line. All characters from the first
non-blank character to the end of the line are deleted and insert mode is
entered.

[n]cmove-cmd

Change from the current position to the position resulting
from n move-cmds (i.e. delete the
indicated region and go into insert mode); if
move-cmd is
c, the line starting from the first non-blank
character is changed.

C

Change from the current position to the end of the line
(i.e. delete to the end of the line and go into insert mode).

[n]x

Delete the next n
characters.

[n]X

Delete the previous n
characters.

D

Delete to the end of the line.

[n]dmove-cmd

Delete from the current position to the position resulting
from n move-cmds;
move-cmd is a movement command (see
above) or d, in which case the current line
is deleted.

This shell is based on the public domain 7th edition Bourne shell clone by
Charles Forsyth and parts of the BRL shell
by Doug A. Gwyn,
Doug Kingston,
Ron Natalie,
Arnold Robbins,
Lou Salkind, and others. The first release
of pdksh was created by
Eric Gisin, and it was subsequently
maintained by John R. MacMillan
<change!john@sq.sq.com>,
Simon J. Gerraty
<sjg@zen.void.oz.au>,
and Michael Rendell
<michael@cs.mun.ca>.
The CONTRIBUTORS file in the source distribution
contains a more complete list of people and their part in the shell's
development.

$(command) expressions are currently parsed by
finding the closest matching (unquoted) parenthesis. Thus constructs inside
$(command) may produce an error. For example,
the parenthesis in ‘x);;’ is interpreted
as the closing parenthesis in ‘$(case x in x);; *);;
esac)’.